Topic 4 - Genetic Information, Variation & Relationships Between Organisms Flashcards
What are the three components of nucleaotides?
A pentose sugar phosphate group and an organic base.
Describe the structure of DNA.
Made up of a deoxyribose sugar a phosphate group and one of four organic bases. It is double stranded and hydrogen bonds between the bases form a helix.
Describe the role of DNA
Carries genetic information and determines our inherited characteristics
Describe the structure of RNA
Made up of a ribose sugar a phosphate group and one of the four organic bases A C G U it is single stranded.
Describe the role of RNA
Transfers genetic information from DNA to ribosomes for protein synthesis
Which bases are purine and which are pyrimidine?
Purine (double ring) = adenine, guanine
Pyramidine (single ring) = cytosine thymine,uracil
How is DNA in eukaryotic cells different from in prokaryotic cells?
Eukaryotic cells = found in the nucleus long and linear. Associated with histone proteins to form chromosomes. Dondria and chloroplast contain prokaryotic like DNA.
Prokaryotic cells = short and circular not associated with proteins called histones.
What is the genetic code?
The order of bases on DNA codons.
What is a codon?
Triplets of bases that code for a particular amino acid
Identify features of the genetic code
Non-overlapping - each triplet is only read once.
Degenerate = more than one chip codes for the same amino acid.
Universal - same bases and sequences used by all species.
What is a gene?
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide.
What is a locus?
The position on a DNA molecule occupied by a gene.
What is an allele?
Different versions of the same gene found at the same locus on the chromosome.
What are exons and introns?
Exons = regions of DNA that code for amino acid sequences.
Introns = regions of DNA that do not code for anything.
What is the genome?
The complete set of genetic information contained in the cells of an organism.
What is the proteome?
The complete set of proteins that can be produced by a cell.
Describe the structure of messenger RNA.
A long single strand. Its base sequence is complementary to the DNA that it was transcribed from.
Suggest advantages of using mRNA rather than DNA for translation.
Shorter and contains uracil = breakdown quickly so no excess polypeptide forms
Single-stranded and linear = why moves along strand and tRNA vines to exposed bases. Contains no introns.
Describe the structure of tRNA.
A single strand of around 80 nucleotides and is folded over into a clover leaf shape. On one end is an anticodon on the opposite end is an amino acid binding site.
What is produced by transcription?
mRNA
Where does transcription take place?
In the nucleus
Outline the process of transcription
DNA uncoils into two strands with exposed bases. One use as a template.
Three nuclear tides lineup next to their complimentary basis and are joined together by RNA polymerase.
What happens to mRNA after transcription?
In eukaryotic cells pre-mRNA must be spliced to remove introns, only the coding regions. Then it moves out of the nucleus and attaches to a ribosome.
What is produced by translation?
Polypeptides
Where does translation take place?
In the cytoplasm
Outline the process of translation
The anticodon of tRNA attaches to complementary bases on the mRNA.
Amino acids bonded to tRNA form peptide bonds continuing to form a polypeptide chain until a codon is reached.
This process requires ATP.
What is a mutation?
An alteration to the DNA base sequence often arise spontaneously during DNA replication
Why might a mutation not lead to change in the amino acid sequence?
The genetic code is degenerate so mutation may end up coding for the same amino acid as the original triplet.
Mutation may occur in intron.
What is a substitution mutation?
When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation meaning no changes occur in the amino acid sequence.
What is a deletion mutation?
When a nucleotide in the DNA sequence is lost. This is more likely to be harmful and significant as it leads to a frame shift which means the entire amino acid sequence will be different.
What is a mutagenic agent? Give examples of this?
Factors that increase the rate of gene mutation. X-rays UV light gamma rays certain chemicals.
What is a polyploidy chromosome mutation?
Where an individual has three or more sets of chromosomes instead of two.
What is chromosome non-disjunction?
When chromosomes fail to separate correctly in meiosis resulting in with one more or less chromosome than normal.
What is meiosis?
A form of cell division that produces four genetically different haploid cells with half the number of chromosomes found in the parent cell.
How does meiosis differ from mitosis?
Meiosis produces four genetically different cells with half the number of chromosomes as the parent cell.
Mitosis produces two genetically identical cells with the same number of chromosomes as the parent cell.
What happens during meiosis one?
- Homologous chromosomes pair to form bivalents.
- Crossing over occurs at chiasmata.
- Cells divide into homologous chromosomes separate randomly each cell contains either maternal or paternal copy.
What happens during meiosis two?
- Independence segregation of sister chromatids.
- Each cell divides again producing four haploid cells.
In which two ways does meiosis produce genetic variation?
- Crossing over during meiosis one
- Independent as segregation of homologous chromosomes and cystic chromatids.
Both results in new combinations of alleles
Define population.
All the organisms of a particular species that live in the same place.
Define genetic diversity.
The total number of different alleles in a population
What advantage does a high genetic diversity provide?
Ability to adapt to a change in environment allows natural selection to occur.
Explain how natural selection results in development of new characteristics
- Random mutations result in new alleles
- Some alleles provide an advantage making an individual more likely to survive and reproduce.
- Their offspring received a new allele and frequency continues to increase over many generations.
What is directional selection?
Because when environmental conditions change individuals with phenotypes suited to the conditions will survive and pass on their genes. Overtime the meaning of the population will move towards these characteristics.
What is stabilising selection?
Occurs when environmental conditions stay the same. Individuals closest to the main of favoured and any new characteristics are selected against. Results in low diversity.
Define a niche
The role of the species within its environment species sharing the same niche will compete with each other.
Define species.
A group of organisms that can interbreed to produce fertile offspring.
What are the advantages of courtship behaviour?
Individuals can recognise sexually mature members of their own species of the opposite sex synchronise meeting form of pair bond and successfully breed.
Define classification.
The process of arranging organisms into groups.
Name the eight groups in the classification hierarchy from largest to smallest
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What system is used to give a species a universal name?
Binomial naming system
What are the two components to a binomial name?
Generic name = the genius the organism belongs to too closely related species will share the same genius.
Specific name = the species of the organism belongs to.
How are binomial names handwritten?
The first letter of the generic name should be capitalised with the rest in lowercase the whole name should be underlined.
What is phylogenetic classification?
The process of arranging organisms into groups based on their evolutionary origins and relationship relationships.
How can we clarify evolutionary relationships between organisms?
Analyse the molecular differences advances in immunology sequencing provides clear pictures of how related to organisms are.
What is hierarchical classification?
Groups within groups with no overlap.
What is bod diversity?
The variety of living organisms. It can be measured in terms of species, diversity, ecosystem, diversity, and genetic diversity.
Define community.
All the different species that live in one area and interact with each other other.
What do the N and n stand for in the index of diversity calculation
N = total number of organisms of all species.
n = total number of organisms of each species.
What impact does farming have on species diversity?
- farmland is typically used for only one species (monoculture).
- Use of pesticides and herbicides
What impact does farming have on genetic diversity?
It decreases it farmers select for certain characteristics which reduces numbers of a different alleles in the population.
How can bod diversity be increased in areas of agriculture?
- Use hedge rows instead of fences.
- Grow different crops in the same area or rotate crops around after season.
- Limit use of pesticides and herbicides
Name four ways in which we can compare genetic diversity between organisms
- Frequency of observable characteristics.
- Base sequence of DNA.
- Base sequence of mRNA.
- Amino acid sequence.
What is meant by gene technology?
Sampling DNA or mRNA in order to read and compare base sequence of organisms. Alternatively the amino acid sequence can be studied as this will also provide information on the organisms mRNA and DNA sequence.
Why do scientists prefer to use gene technology instead of observation?
Simply inferring DNA differences by observing an organisms characteristics is not reliable, the characteristics could be coded by more than one gene or could be influenced by the environment.
What is meant by interspecific and intraspecific variation.
Interspecific = differences between individuals of different species
Intraspecific = differences between individuals of the same species.
What is sampling?
Selecting a group of individuals to measure what will represent the whole target population.
How can random sampling be achieved?
Create a grid for your sample area and then randomly generate coordinates where a quadrat or transact can be placed. Repeat until required sample sizes reached.
